1. Field of the Invention
This invention relates to a travel assembly suited for arrangement on a vehicle such as a mining dump truck and having a travel motor and a planetary speed reduction mechanism for transmitting rotation of the travel motor at a lower rotational speed.
2. Description of the Related Art
As a conventional technology of this sort, there is one disclosed in Ciszak et al. U.S. Patent Application Publication No. 2004/0065169 A1. This conventional technology is provided with a travel motor, a planetary speed reduction mechanism for transmitting rotation of the travel motor at a lower rotational speed, a spindle forming an axle, a hub arranged on an outer side of the spindle and splined to the spindle, and a wheel supported on the hub via tapered roller bearings and rotatable by the planetary speed reduction system. The planetary speed reduction mechanism is provided with a sun gear rotatable by a shaft of the travel motor, planet gears for rotating the wheel in response to rotation of the sun gear, stepped pins forming rotary shafts for the planetary gears, a carrier supporting the stepped pins thereon and splined to the above-mentioned hub, and bolts fixedly securing the above-mentioned stepped pin on the carrier. The conventional travel assembly equipped with such a construction as described above is used for the rotational drive or the like of a tire of a mining dump truck.
With respect to the above-mentioned conventional technology, there is an outstanding desire for a construction that eliminates the hub splined to both the spindle and the planetary speed reduction mechanism with a view to increasing the strength of the spindle and cutting down the manufacturing cost, etc. To adopt such a non-hub construction as described above, it may be contemplated to directly spline the spindle and the carrier to each other. When constructed so, however, heads of the bolts that fixedly secure the stepped pins on the carrier are located opposite the proximal tapered roller bearing, leading to a potential problem that, when the bolts become loose by vibrations transmitted to the stepped pins, carrier and bolts, the heads of the bolts may come into contact with the proximal tapered roller bearing and may damage the proximal tapered roller bearing.